Make sure when --es.num-replicas=0, ES indexes have numReplicas set to 0 instead of 1

[bharat-p]

Resolves #369

See original PR#371 (which I messed up while updating my outdated branch) for past discussion around this.

ES number of replicas was getting set to 1 even when specifying --es.num-replicas=0 when starting collector and query, which caused a single node ES cluster to be always in "yellow" state with unassigned shards.

Before fix:

output of localhost:9200/_cluster/health?pretty

curl "localhost:9200/_cluster/health?pretty"                                                         [Mar 22, 7:06 PM]
{
  "cluster_name" : "jaeger-cluster",
  "status" : "yellow",
  "timed_out" : false,
  "number_of_nodes" : 1,
  "number_of_data_nodes" : 1,
  "active_primary_shards" : 10,
  "active_shards" : 10,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 10,
  "delayed_unassigned_shards" : 0,
  "number_of_pending_tasks" : 0,
  "number_of_in_flight_fetch" : 0,
  "task_max_waiting_in_queue_millis" : 0,
  "active_shards_percent_as_number" : 50.0
}

output of http://localhost:9200/jaeger-span-2018-03-23/_settings?pretty

curl "http://localhost:9200/jaeger-span-2018-03-23/_settings?pretty"                                 [Mar 22, 7:07 PM]
{
  "jaeger-span-2018-03-23" : {
    "settings" : {
      "index" : {
        "mapping" : {
          "nested_fields" : {
            "limit" : "50"
          }
        },
        "number_of_shards" : "5",
        "provided_name" : "jaeger-span-2018-03-23",
        "mapper" : {
          "dynamic" : "false"
        },
        "creation_date" : "1521770836101",
        "requests" : {
          "cache" : {
            "enable" : "true"
          }
        },
        "number_of_replicas" : "1",
        "uuid" : "GxfUsJRzQP25QyFw1M0gGg",
        "version" : {
          "created" : "5050399"
        }
      }
    }
  }
}

Verified after fix:
output of http://localhost:9200/_cluster/health?pretty

{
  "cluster_name" : "jaeger-cluster",
  "status" : "green",
  "timed_out" : false,
  "number_of_nodes" : 1,
  "number_of_data_nodes" : 1,
  "active_primary_shards" : 10,
  "active_shards" : 10,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 0,
  "delayed_unassigned_shards" : 0,
  "number_of_pending_tasks" : 0,
  "number_of_in_flight_fetch" : 0,
  "task_max_waiting_in_queue_millis" : 0,
  "active_shards_percent_as_number" : 100.0
}

After fix output of http://localhost:9200/jaeger-span-2018-03-23/_settings?pretty

curl "http://localhost:9200/jaeger-span-2018-03-23/_settings?pretty"                                [Mar 22, 7:02 PM]
{
  "jaeger-span-2018-03-23" : {
    "settings" : {
      "index" : {
        "mapping" : {
          "nested_fields" : {
            "limit" : "50"
          }
        },
        "number_of_shards" : "5",
        "provided_name" : "jaeger-span-2018-03-23",
        "mapper" : {
          "dynamic" : "false"
        },
        "creation_date" : "1521770529358",
        "requests" : {
          "cache" : {
            "enable" : "true"
          }
        },
        "number_of_replicas" : "0",
        "uuid" : "rMVWSG4uRgmEQDlXyKu-DA",
        "version" : {
          "created" : "5050399"
        }
      }
    }
  }
}

[coveralls]

Coverage remained the same at 100.0% when pulling 21f6b64 on bharat-p:bharat-es-replica-fix into 83d06da on jaegertracing:master.

[pavolloffay]

@bharat-p thanks!

[pavolloffay]

At some point, we should consider externalizing all ES configuration.